Vanadium-containing alloying additive for steel

ABSTRACT

VANADIUM-CONTAINING ALLOYING ADDITIVE FOR STEELS IS OBTAINED FROM VANADIC ACID, I.E., VANADIUM PENTAOXIDE OR VANADIUM PENTOXIDE-CONTAINING COMPOSITIONS IN A ONE STAGE PROCESS WITHOUT THE USE OF VACUUM TREATMENT BY THE SOLID-STATE REDUCTION OF VANADIC ACID WITH CARBON UNDER ATMOSPHERIC CONDITIONS AT TEMPERTURES OF FROM 1200 TO 1500*C., TO PRODUCE A SUBSTANCE OF THE FOLLOWING COMPOSITION:   PERCENT , FROMVANADIUM 70 TO 85 OXYGEN 2 TO 10 CARBON 5 TO 20 NITROGEN 0.5 TO 4   TO TAKE UP RESIDUAL OXYGEN IN A STEEL-MAKING BATH INTO WHICH SAID ADDITRIVE IS ADDED, SILICON OR ALUMINUM OR A FERROSILICON MAY BE INCORPORATED IN THE ADDITIVE. THE USE OF SUCH AN ADDITIVE IN A STEEL MAKING PROCESS IS PARTICULARLY ADVANTAGEOUS IN THAT THE ADDITIVE DISSOLVES WELL IN THE STEEL BATH DESPITE RESIDUAL OXYGEN IN THE STEEL MAKING BATH. THE HIGH DENSITY OF THE ADDITIVE RESULTS IN IT TAKING UP A POSITION IN THE STEEL BATH BETWEEN THE SLAG AND THE BATH SURFACE, THEREBY EFFECTING A FURTHER IMPROVEMENT IN SOLUTION.

United States Patent Oflice- Patented Feb. 23, 1971 3,565,610VANADIUM-CONTAINING ALLOYING ADDITIVE FOR STEEL Hans Joachim Retelsdorf,Nuremberg Katzwang, and

Rudolf Fichte, Nuremberg, Germany, assignors to Gesellschaft fiirElektrometallurgie m.b.H., Dusseldorf, Germany No Drawing. Filed May 22,1968, Ser. No. 731,272 Claims priority, application Germany, May 29,1967, P 15 58 503.2 Int. Cl. C22c 35/00 US. Cl. 75-133 7 Claims ABSTRACTOF THE DISCLOSURE Vanadium-containing alloying additive for steels isobtained from vanadic acid, i.e., vanadium pentoxide or vanadiumpentoxide-containing compositions in a one stage process without the useof vacuum treatment by the solid-state reduction of vanadic acid withcarbon under atmospheric conditions at temperatures of from 1200 to 1500C., to produce a substance of the following composition:

Percent, from- Vanadium 70 to 85 Oxygen 2 to 10 Carbon 5 to 20 Nitrogen0.5 to 4 To take up residual oxygen in a steel-making bath into whichsaid additive is added, silicon or aluminum or a ferrosilicon may beincorporated in the additive.

The use of such an additive in a steel making process is particularlyadvantageous in that the additive dissolves well in the steel bathdespite residual oxygen in the steel making bath. The high density ofthe additive results in it taking up a position in the steel bathbetween the slag and the bath surface, thereby effecting a furtherimprovement in solution.

This invention relates to a vanadium-containing substance produced in aone-stage reduction process, which is useful as an alloying agent forsteel production.

It is known to alloy steel with vanadium by adding to the steel bathferrovanadium having a vanadium content in the range of from 50 to 80%thereof. It is also known to add the vanadium in the form ofcarbon-containing ferrovanadium containing from 3 to of carbon, thevanadium being combined therein in the form of carbide. It has recentlybecome known that a vanadium carbide (V C) produced in the solid statecan be used as an alloying agent. It is claimed that this product hasthe advantage of greater economy in comparison with ferrovanadium, whichis produced by the aluminothermal reduction of vanadium pentoxide.Nevertheless its production is expensive and time-consuming, severalprocess stages being required to produce the V C. Thus, in the firststage, vanadium pentoxide or ammonium vanadate is reduced to vanadiumtrioxide, which, with the corresponding quantity of carbon, is thenreduced to vanadium carbide under reduced pressure over a long period ata temperature between 1200 and 1400 C.

The invention provides a process whereby a vanadiumcontaining alloyingadditive derived from vanadic acid, i.e., vanadium pentoxide or acomposition containing a major proportion of vanadium pentoxide, whichis useful as an alloying agent for steel production, can be produced inone stage and without vacuum treatment directly fromvanadic acidcompounds. One such compound is vanadium pentoxide itself, which on anindustrial scale is precipitated from a sodium vanadate solution, dried,calcined or melted, the product containing impurities (which may amountto up to 10% individually or together) such as alkali and ammoniuminduced in the precipitate stage. Another such compound is ammoniumrnetavanadate, which decomposes at a temperature in excess of 100 C.with the liberation of ammonium salts of vanadium pentoxide or vanadiumpentoxide associated with lower-valency oxides.

The invention consists of a vanadium-containing substance, useful as analloying additive for steels, which is produced in the solid-statereduction of vanadic acid with carbon under atmospheric conditions attemperatures of 1200-1 5 00 C., having a composition:

Percent, from Vanadium 70 to 85 Oxygen 2 to 10 Carbon 5 to 20 Nitrogen0.5 to 4 The term carbon used in the said composition includes compoundssuch as carbon black, charcoal, coal, coke and electrode coke.

The vanadium-containing substance this obtained dissolves easily insteel baths, despite the residual oxygen content. Reaction betweencarbon and oxygen takes place in the steel bath, the CO containing gasesthus generated causing agitation of the melt leading to improveddistribution of the vanadium throughout the steel. This is particularlyimportant due to the small proportion of vanadium used as an alloyingmaterial.

The alloying agent according to the invention is obtainable in the formof briquettes or pellets, or a porous sinter, which can be addeddirectly to the steel bath.

To facilitate the reaction of the residual oxygen being effected in thesteel bath, it may be advantageous to incorporate a further reducingagent in the alloying agent, for example silicon and/or aluminium, whichmay be in the form of a known ferro alloy, such as ferro silicon, ferroaluminium or ferro silicon aluminium. Carbon may also be incorporated atthe same time.

The additions of silicon and/ or aluminium and possibly carbon must, ofcourse, be such that they are only enough to reduce the residual oxygenand do not cause impermissible carburisation or an undesirable increasein these contents in the steel bath.

The alloying agent according to the invention may be introduced into thesteel bath in comminuted form, in metal or combustible containers, forexample tin boxes, or bags of paper or of plastics material or the like.If desired it may also be blown into the bath using known techniques.

Briquettes of the alloying agent may be obtained using known techniquesof briquetting. The briquettes thus obtained are of high density andwhich is greater than the density of conventional slags, so that theylie between the bath slag and the bath surface during solution whichassists the act of solution.

The following examples of the invention are provided:

EXAMPLE 1 kg. of industrial vanadic acid containing 84.8% of V 0 and4.5% of H 0, the remainder being precipitationinduced impurities; and 30kg. of fine coke containing, 91% of carbon in the dried state and 3.4%of H 0; were mixed with about 10% of water to prevent dust loss, andkernel oil was added as a binder. Pellets of from 4 to 6 mm. diameterwere formed from this mixture on a pelletising dish with the addition ofmore water. The pellets were then put in the reduction furnace andcalcined for six hours at 1350 C. The reducing atmosphere was obtainedby covering the pellets with granulated coke. To prevent the entry ofair, closed clay graphite crucibles were used, the crucibles passingthrough a tunnel furnace. With a charge of 125 kg. of pellets (dry)there were obtained 64.5 kg. of alloying agent containing 73.2% ofvanadium, 16.5% of carbon, 1.8% of oxygen and 2.0% of nitrogen, theremainder consisting of impurities, being ash components of coke.

The apparent density of these pellets was 0.71 kg./dm. After comminutionand pressing into briquettes, the density was from 3 to 3.4 kg./dm.

EXAMPLE 2 Pellets of a vanadium product containing less carbon than thatobtained in Example 1, was produced in the same way as Example 1, from100 kg. of vanadic acid and 22.5 kg. of coke.

60 kg. of final product contained 79.2% of vanadium, 6.9% of carbon,6.1% of oxygen and 2.9% of nitrogen.

This product contained too much oxygen in relation to the carboncontent, and an alloying agent was prepared from the said product byadmixing therewith 5.3 kg. of pulverised 75% ferrosilicon and pressinginto briquettes with kernel oil binder, the briquettes having a densityof 3.1 kg./dm.

The alloying agent contained 72.8% of vanadium, 6.3% of carbon, 6.1% ofsilicon, 2.5% of iron, 5.6% of oxygen and 2.7% of nitrogen.

The briquettes prepared according to Examples 1 and 2 were added tosteel baths having a temperature of 80 C. After two to three minutes thebriquettes dissolved and a uniform distribution of the 0.15% of vanadiumwas achieved in the steel bath, corresponding to a vanadium take up ofover 90%.

The absence of the use of expensive reduced pressure stages in preparingthe alloying agents according to the invention means that the cost ofpreparation is reduced, and the frequent repair of reduced-pressureapparatus owing to the high temperatures used, is avoided. The reactiontimes required for the production of the agent according to theinvention are, moreover, much shorter, and the production of thealloying agent is not restricted to the use of any particular type offurnace. All that is required is that the reaction temperatures can bereached and the calcination material can be subjected to a reducingatmosphere. Thus, for example, reducing rotary tubular kilns orcontinuously-burning furnaces may be used.

What is claimed is:

1. A vanadium-containing alloying additive for steels, obtained by thesolid-state reduction of vanadic acid with carbon under atmosphericconditions at a temperature in the range 12001500 C., the said alloyingadditive having a composition; 7

Percent, fr0rn Vanadium to 85 Oxygen 2 to 10 Carbon 5 to 20 Nitrogen 0.5to 4 2. A vanadium-containing alloying additive as claimed in claim 1,containing at least one reducing agent selected from the classconsisting of silicon, aluminum, ferrosilicon, ferroaluminum andferrosilicon aluminum.

3. A process of preparing an alloy steel bath, and incorporating in thesaid steel bath a vanadium-containing alloying additive having acomposition:

Percent, from Vanadium 70 to 85 Oxygen 2 to 10 Carbon 5 to 20 Nitrogen0.5 to 4 4. A process according to claim 3, in which the saidvanadium-containing alloying additive contains a reducing agent selectedfrom the class consisting of silicon, aluminum, ferrosilicon,ferroaluminum and ferrosilicon aluminum.

5. A process according to claim 3, in which the said vanadium-containingalloying additive is added to the said steel bath in the form of apressed mass selected from the class consisting of briquettes, pelletsand porous sinter.

6. A process according to claim 3, in which carbon is incorporated inthe said steel bath in addition to the said vanadium-containing alloyingelement, in a proportion sufiicient to effect reduction of residualoxygen in the said steel bath.

7. A process according to claim 3, in which the said vanadium-containingalloying additive is added to the said steel bath in comminuted formcontained in a container.

References Cited UNITED STATES PATENTS 1,119,643 12/1914 Saklatwalla 1331,697,759 1/1929 Feild 75133 1,811,698 6/1931 Saklatwalla 751331,901,367 3/1933 Gustafsson 75133.5 2,381,675 8/1945 Linz 75-133X2,576,763 11/1951 Linz 75-133 L. DEWAYNE RUTLEDGE, Primary Examiner I.E. LEGRU, Assistant Examiner 11.5. C1. X.R. 7l 9

